1. Field of the Invention
The present invention relates to a method of additionally attaching a new disk system (migration destination disk system) to a storage area network (hereafter referred to as SAN) and migrating data from an old disk system (migration source disk system), which is already connected to the SAN, to that new disk system and a device thereof.
2. Description of Related Art
Conventional computer systems are configured with a plurality of servers connected by a network such as a LAN and disk units are directly connected to each computer. The data inside each disk unit was managed by the directly connected server. In other words, data was managed in a distributed condition.
However, the SAN which adopts a configuration in which a plurality of servers, a plurality of disk units, backup units, etc. are connected by a switch or hub has recently become a hot topic. Fiber channels are used to physically connect these units to a switch or hub. The advantages of configuring a system using a SAN are superior scalability and the realization of reduced management cost since unified management can be performed by integrating data distributed over a plurality of disk units. Consequently, a SAN is well suited to a large-scale system. Because many resources are interconnected with a SAN, the management of these resources is an important topic. The management of a logical volume (such as backup), as the management of a disk unit, is one example of that. At present, these management methods are being studied by the SNIA (Storage Networking Industry Association) and NSIC (National Storage Industry Consortium).
On the other hand, U.S. Pat. No. 5,680,640 discloses a system and method of migrating data from a first data storage system to a second data storage system. A summary of that is as follows. A first data storage system already connected to a host, network or other data processing system is detached from the aforementioned host and connected to a second data storage system. The aforementioned second data storage system is connected to the aforementioned host or aforementioned data processing system. The aforementioned second data storage system contains a data map or data table that indicates which data element is stored in the aforementioned second storage system and which data in the aforementioned first data storage system has been copied to the aforementioned second storage system. When the aforementioned host, aforementioned network or aforementioned data processing system issues a request for data to the aforementioned second storage system, the aforementioned second data storage system judges whether that data has been stored in the aforementioned second data storage system or in the aforementioned first storage system. If the data has been stored in the aforementioned second data storage system, that data can be used by the host, etc. If the data is not stored in the aforementioned second data storage system, the aforementioned second data storage system issues a request to the aforementioned first data storage system, and that data can be used by the aforementioned host, etc. Then, the aforementioned second data storage system writes that data to its own system and updates the aforementioned data map or aforementioned data table. When the aforementioned second data storage system is not busy, it scans the aforementioned data map or aforementioned data table, determines which data of the aforementioned first data storage system has not yet been copied into its own system, and executes the copying of that data and updating of the aforementioned data map or aforementioned data table.
According to the data migration system and method disclosed in U.S. Pat. No. 5,680,640, independent from the aforementioned host, it is possible to execute data migration from the aforementioned first data storage system to the aforementioned second data storage system.
However, in the aforementioned data migration system and method, when the aforementioned second data storage system is utilized, the procedure of detaching the aforementioned first data storage system from the aforementioned host, connecting it to the aforementioned second data storage system, and connecting the aforementioned second data storage system to the aforementioned host is necessary. Consequently, at least during the interval beginning when the aforementioned first data storage system is detached from the aforementioned host until the aforementioned second data storage system is connected to the aforementioned host and the aforementioned first storage system, the aforementioned host cannot issue I/O (Input/Output) requests. In addition, during that interval it is necessary to temporarily suspend applications or other programs on the aforementioned host that use the aforementioned first data storage system. To further suppress costs associated with data migration, it is necessary to further reduce the time when I/O requests cannot be issued and the time when applications are suspended.
In addition, in the aforementioned data migration system and method, to connect the aforementioned first data storage system to the aforementioned second data storage system, a channel must be newly provided to each data storage system.
Further, in U.S. Pat. No. 5,680,640, a data migration system and method in a SAN environment are not disclosed.